They found a special transmembrane protein encoded by rat genes and named it neu gene; later, scientists discovered that the structure of neu was similar to ERBB2/HER2 gene and successfully cloned HER2 and measured the complete sequence; in 1987, it had been found that there existed excessive HER2 amplification or overexpression in some breast cancer patients, leading to uncontrolled tumorigenesis, lower survival rates, and faster recurrence [10,11,12,13]. The gene discussed is ERBB2; the disease is breast cancer.